This project focuses on the anatomical properties and organization of cells in the primate visual system with emphasis on the retina and the visual cortex. The studies include (1) the anatomical association of outer-retinal cells selectively stained with tissue-reactive dyes and (2) the distribution pattern of cones in the retina of human donors who have a diagnosis of diabetic retinopathy. Systematic light-microscopy of the anatomical association of macaque retina blue cones and horizontal and bipolar cells, with selective staining by several tissue-reactive dyes, has provided information on the probable circuitry of the blue-sensitive cone pathway of primate retina. Retinal cone studies of human eye donors with a history of diabetes continue. There is evidence that the cone population from the retinas of these donors has a point pattern resembling that of cones selectively stained by tissue-reactive dyes. Although such dyes were not injected in the eyes from diabetic donors, in vitro staining with more conventional dyes shows a differential labeling of the receptors. Some cones are more densely stained than other cones, and the point pattern is similar to that of the blue-sensitive cones of the primate retina.